'Oh, er ... 20 shekels,' says the salesman.

'What? There you are.'

'Wait a minute. We're supposed to haggle.'

'No, no, I haven't got time.'

'Bert! This bloke won't haggle.'

'Won' 'aggle?' cries an incredulous, threatening, two-metre-tall Bert.

'Now look, are you telling me that's not worth 20 shekels?' asks the shifty salesman, gesticulating to an imaginary crowd. 'Look at it, feel the quality. That's none of your goat.'

'I'll give you 10,' says a terrified Brian.

'Ten! Are you trying to insult me; me with a poor, dying grandmother? Seventeen. My last word, I won't take a penny less or strike me dead.'

'Sixteen.'

'Done.'

And lo, it came to pass that haggling was born. For the tourist not being hunted by a Roman centurion or modern equivalent, and with more time to peruse the wares in market, mall or ethnic village, haggling is essential; as increasing numbers of people travel around our commerce-driven world it will again become a survival skill - as it was in Monty Python's Life of Brian.

So you might as well learn how to do it. If, like the Hong Kong party of guided tourists that recently visited Tunisia and was continually mistaken for a group of Japanese, you are too polite to haggle, you will be ripped off. Vendors from Spitalfields Market in London to Namdaemun Market in Seoul expect to haggle and set their initial prices accordingly, meaning you should not feel uncomfortable about the process. Fling cash at a stallholder because you feel embarrassed about bargaining and you make life tougher for the next customer.

Do your homework. What exactly do you want to buy? That fetching stuffed donkey wearing the sombrero, the genuine, spangly bullfighter's cloak or the '... this lousy T-shirt' T-shirt? Having decided your flat needs a donkey, talk to other browsers and find out what represents a fair price. And while you're at it, what is your priority? Price, probably, but for the salesman it might be a quick transaction, particularly if you are in Asia and he is desperate to make that auspicious inaugural sale of the day.

Staying at the Shangri-La, are you? Lovely. Tell that to a stallholder and watch him inflate his starting price 300 per cent. Purveyors of all goods will raise their tariffs if they believe you are wealthy. Tell them you are guests at some nearby pestilential guesthouse instead and you can bank on a less ludicrous opening gambit. (This tactic does not work for Americans, whom, it is believed, possess unlimited natural wealth even tatty backpacks cannot obscure. In their honour, the insanely exaggerated opening amount has been named the 'American price'. In Hong Kong, particularly in the camera shops of Tsim Sha Tsui and Causeway Bay, it is known as the 'gweilo price'. This wider application also extends to the Japanese; see above.)

Talking of prices, how much do you want to pay? Unless you're Bill Gates, everything has a price limit. Set yourself a maximum and stick to it, even if it means you miss out on that spleen-splittingly funny Indonesian carving with the enormous penis. You'll find another at the next stall. Free of inflationary worries, the vendor will begin trading at that laughably high price you've just been warned about. Make your counter offer, which can be laughably low. When he feigns insult and mentions his poor, dying grandmother, walk away. The salesman is bound to follow, making two or three offers, the price falling with each.

When you're about to hit the road, you can avoid having to haggle altogether by going through legitimate channels. The first-floor entrance to the arrivals terminal at Bangkok International Airport, for example, attracts taxis offering a way to beat the queues downstairs, where all the mugs seem to line up for a ride. Take one of these cabs, however, and you may find yourself swindled out of 200 baht: it is illegal for drivers to wait there, and any cabbie happy to take his chances with the police won't baulk at ripping off a farang or six. Join the throng downstairs, pay at the booth, take the resultant slip of paper bearing your destination and give it to the driver. Negotiations don't enter into it.

Enticements, known in other trading circles as bribes, may be offered in that Aladdin's junkyard of a carpet showroom in old Dubai. Accepting coffee, tea or cakes does not signify acceptance of price, no matter how hard the salesman leans on you later. Feign lack of interest, reject his complaints and, while you're at it, politely refuse the assistance of the friendly local who offers to help. He's the salesman's brother-in-law.

Having a few negotiating tricks up your sarong is all very well and can add to the fun in the souk, but cultural concerns demand you bargain responsibly. If you make an offer on that grotesque elephant's foot umbrella stand, the vendor is entitled to think you are serious about buying. Don't waste your time or his with frivolous banter.

Tourists can be adept at making themselves look foolish, and not just at full-moon parties on Koh Phangan. Not everything is up for negotiation. Some purchases do have fixed prices, such as anything sold in supermarkets, train tickets, restaurant meals and museum admissions. If you feel you're being fleeced, casually ask a local what they're paying.

There may be room for manoeuvre in the jewellery store or leather emporium, but do you have to squeeze one last lek out of that Albanian fruit seller? A meagre handful of coins could keep an independent shopkeeper in business - or make all the difference to that poor, dying grandmother.